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hpr1951 :: Some additional Bash tips

by: Dave Morriss

Publication date: 2016-01-25

Usage: http://creativecommons.org/licenses/by-sa/3.0

Topics: Bash, expansion, arithmetic expansion, shell arithmetic, number base

Contributor: HackerPublicRadio

Language: English

Summary: More about expansion in Bash: this time arithmetic expansion
Series: Bash Scripting
Source: http://hackerpublicradio.org/eps.php?id=1951

Some additional Bash tips

Expansion

As we saw in the last episode 1903 there are seven types of expansion applied to the command line in the following order:

Brace expansion (we looked at this subject in episode 1884)
Tilde expansion (seen in episode 1903)
Parameter and variable expansion (this was covered in episode 1648)
Command substitution (seen in episode 1903)
Arithmetic expansion
Word splitting
Pathname expansion

There is also another, process substitution, which occurs after arithmetic expansion on systems that can implement it.

We will look at one more of these expansion types in this episode but since there is a lot to cover, we'll continue in a later episode.

I have written out a moderately long set of notes about this subject and these are available here https://hackerpublicradio.org/eps/hpr1951_full_shownotes.html.

Audio Note

This time, in the spirit of experimentation and as a way of learning Audacity I processed my audio thus:

Turned the stereo tracks to mono
Used a Noise Gate plug-in to reduce background noise (after "training" it on some silence)
Performed a Truncate Silence pass to reduce the length of pauses
Applied a small amount of amplification

Let me know if this had any positive or negative effects on the end product.